Method and apparatus for beam detection in a wireless communication system

ABSTRACT

A method and apparatus for beam detection in a wireless communication system. In one embodiment, the method includes the UE initiating a RA procedure. The method also includes the UE transmitting multiple RA preambles to a base station of the cell at different occasions for the base station to determine a beam set of the UE. The method further includes the UE starts monitoring a PDCCH for RA response reception from the base station after finishing transmissions of the multiple RA preambles.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and is a continuation of U.S.application Ser. No. 15/004,370, filed on Jan. 22, 2016, entitled“METHOD AND APPARATUS FOR BEAM DETECTION IN A WIRELESS COMMUNICATIONSYSTEM”, which claims the benefit of U.S. Provisional Patent ApplicationSer. No. 62/107,792 filed on Jan. 26, 2015, U.S. Provisional PatentApplication Ser. No. 62/107,814 filed on Jan. 26, 2015, and U.S.Provisional Patent Application Ser. No. 62/166,368 filed on May 26,2015. The entire disclosure of U.S. application Ser. No. 15/004,370, theentire disclosure of U.S. Provisional Patent Application Ser. No.62/107,792, the entire disclosure of U.S. Provisional Patent ApplicationSer. No. 62/107,814 and the entire disclosure of U.S. Provisional PatentApplication Ser. No. 62/166,368 are incorporated herein in theirentirety by reference.

FIELD

This disclosure generally relates to wireless communication networks,and more particularly, to a method and apparatus for beam detection in awireless communication system.

BACKGROUND

With the rapid rise in demand for communication of large amounts of datato and from mobile communication devices, traditional mobile voicecommunication networks are evolving into networks that communicate withInternet Protocol (IP) data packets. Such IP data packet communicationcan provide users of mobile communication devices with voice over IP,multimedia, multicast and on-demand communication services.

An exemplary network structure for which standardization is currentlytaking place is an Evolved Universal Terrestrial Radio Access Network(E-UTRAN). The E-UTRAN system can provide high data throughput in orderto realize the above-noted voice over IP and multimedia services. TheE-UTRAN system's standardization work is currently being performed bythe 3GPP standards organization. Accordingly, changes to the currentbody of 3GPP standard are currently being submitted and considered toevolve and finalize the 3GPP standard.

Furthermore, EU started the METIS project in November 2012 to lay thefoundation of 5G, the next generation mobile and wireless communicationssystem. The main technical objectives (or 5G requirements) include thefollowing:

-   -   1000 times higher mobile data volume per area;    -   10 to 100 times higher number of connected devices;    -   10 to 100 times higher user data rate;    -   10 times longer battery life for low power massive machine        communications (MMC);    -   5 times reduced End-to-End latency (<5 ms).

It is clear the above requirements demand much higher system capacitythan what can be offered by the legacy systems. Thus, a new radio accesstechnology can be expected to fulfill these requirements.

SUMMARY

A method and apparatus for beam detection in a wireless communicationsystem. In one embodiment, the method includes the UE initiating arandom access (RA) procedure. The method also includes the UEtransmitting multiple RA preambles to a base station of the cell atdifferent occasions for the base station to determine a beam set of theUE. The method further includes the UE starts monitoring a PhysicalDownlink Control Channel (PDCCH) for RA response reception from the basestation after finishing transmissions of the multiple RA preambles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of a wireless communication system according toone exemplary embodiment.

FIG. 2 is a block diagram of a transmitter system (also known as accessnetwork) and a receiver system (also known as user equipment or UE)according to one exemplary embodiment.

FIG. 3 is a functional block diagram of a communication system accordingto one exemplary embodiment.

FIG. 4 is a functional block diagram of the program code of FIG. 3according to one exemplary embodiment.

FIG. 5 illustrates a contention-based Random Access procedure.

FIG. 6 illustrates a contention-free Random Access procedure.

FIG. 7 is a reproduction of FIG. 5.1-1 of 3GPP TS 36.300 V12.5.0.

FIG. 8 is a reproduction of FIG. 5.1-2 of 3GPP TS 36.300 V12.5.0.

FIG. 9 is a reproduction of Table 5.1-1 of 3GPP TS 36.300 V12.5.0.

FIG. 10 is a reproduction of FIG. 6.2.2-1 of 3GPP TS 36.211 V12.5.0.

FIG. 11 is a reproduction of Table 6.2.3-1 of 3GPP TS 36.211 V12.5.0.

FIG. 12 illustrates a physical subframe structure for a UDN (Ultra-DenseNetwork) system.

FIG. 13 is a diagram according to one exemplary embodiment.

FIG. 14 is a message flow diagram according to one exemplary embodiment.

FIG. 15 is a message flow diagram according to one exemplary embodiment.

FIG. 16 is a timing diagram according to one exemplary embodiment.

FIG. 17 is a flow chart according to one exemplary embodiment.

FIG. 18 is a flow chart according to one exemplary embodiment.

FIG. 19 is a flow chart according to one exemplary embodiment.

FIG. 20 is a flow chart according to one exemplary embodiment.

FIG. 21 is a flow chart according to one exemplary embodiment.

FIG. 22 is a flow chart according to one exemplary embodiment.

FIG. 23 is a flow chart according to one exemplary embodiment.

FIG. 24 is a flow chart according to one exemplary embodiment.

FIG. 25 is a flow chart according to one exemplary embodiment.

FIG. 26 is a flow chart according to one exemplary embodiment.

DETAILED DESCRIPTION

The exemplary wireless communication systems and devices described belowemploy a wireless communication system, supporting a broadcast service.Wireless communication systems are widely deployed to provide varioustypes of communication such as voice, data, and so on. These systems maybe based on code division multiple access (CDMA), time division multipleaccess (TDMA), orthogonal frequency division multiple access (OFDMA),3GPP LTE (Long Term Evolution) wireless access, 3GPP LTE-A orLTE-Advanced (Long Term Evolution Advanced), 3GPP2 UMB (Ultra MobileBroadband), WiMax, or some other modulation techniques.

In particular, the exemplary wireless communication systems devicesdescribed below may be designed to support the wireless technologydiscussed in the various documents, including: “DOCOMO 5G White Paper”by NTT Docomo, Inc. Furthermore, the exemplary wireless communicationsystems devices described below may be designed to support one or morestandards such as the standard offered by a consortium named “3rdGeneration Partnership Project” referred to herein as 3GPP, including:R2-145410, “Introduction of Dual Connectivity”, NTT Docomo, Inc., NEC;TS 36.321 V12.3.0, “E-UTRA MAC protocol specification”; TS 36.213V12.3.0, “E-UTRA Physical layer procedures”; TS 36.300 V12.5.0, “E-UTRAand E-UTRAN Overall description”; TS 36.211 V12.5.0, “E-UTRA Physicalchannels and modulation”; and METIS Public Deliverable D2.4 “Proposedsolutions for new radio access”. The standards and documents listedabove are hereby expressly incorporated by reference in their entirety.

FIG. 1 shows a multiple access wireless communication system accordingto one embodiment of the invention. An access network 100 (AN) includesmultiple antenna groups, one including 104 and 106, another including108 and 110, and an additional including 112 and 114. In FIG. 1, onlytwo antennas are shown for each antenna group, however, more or fewerantennas may be utilized for each antenna group. Access terminal 116(AT) is in communication with antennas 112 and 114, where antennas 112and 114 transmit information to access terminal 116 over forward link120 and receive information from access terminal 116 over reverse link118. Access terminal (AT) 122 is in communication with antennas 106 and108, where antennas 106 and 108 transmit information to access terminal(AT) 122 over forward link 126 and receive information from accessterminal (AT) 122 over reverse link 124. In a FDD system, communicationlinks 118, 120, 124 and 126 may use different frequency forcommunication. For example, forward link 120 may use a differentfrequency then that used by reverse link 118.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the access network. Inthe embodiment, antenna groups each are designed to communicate toaccess terminals in a sector of the areas covered by access network 100.

In communication over forward links 120 and 126, the transmittingantennas of access network 100 may utilize beamforming in order toimprove the signal-to-noise ratio of forward links for the differentaccess terminals 116 and 122. Also, an access network using beamformingto transmit to access terminals scattered randomly through its coveragecauses less interference to access terminals in neighboring cells thanan access network transmitting through a single antenna to all itsaccess terminals.

An access network (AN) may be a fixed station or base station used forcommunicating with the terminals and may also be referred to as anaccess point, a Node B, a base station, an enhanced base station, anevolved Node B (eNB), or some other terminology. An access terminal (AT)may also be called user equipment (UE), a wireless communication device,terminal, access terminal or some other terminology.

FIG. 2 is a simplified block diagram of an embodiment of a transmittersystem 210 (also known as the access network) and a receiver system 250(also known as access terminal (AT) or user equipment (UE)) in a MIMOsystem 200. At the transmitter system 210, traffic data for a number ofdata streams is provided from a data source 212 to a transmit (TX) dataprocessor 214.

In one embodiment, each data stream is transmitted over a respectivetransmit antenna. TX data processor 214 formats, codes, and interleavesthe traffic data for each data stream based on a particular codingscheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM)selected for that data stream to provide modulation symbols. The datarate, coding, and modulation for each data stream may be determined byinstructions performed by processor 230.

The modulation symbols for all data streams are then provided to a TXMIMO processor 220, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulationsymbol streams to N_(T) transmitters (TMTR) 222 a through 222 t. Incertain embodiments, TX MIMO processor 220 applies beamforming weightsto the symbols of the data streams and to the antenna from which thesymbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transmitters 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are receivedby N_(R) antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective receiver (RCVR) 254 a through254 r. Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by RX data processor 260 is complementary to thatperformed by TX MIMO processor 220 and TX data processor 214 attransmitter system 210.

A processor 270 periodically determines which pre-coding matrix to use(discussed below). Processor 270 formulates a reverse link messagecomprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 238, whichalso receives traffic data for a number of data streams from a datasource 236, modulated by a modulator 280, conditioned by transmitters254 a through 254 r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240, and processed by a RX data processor242 to extract the reserve link message transmitted by the receiversystem 250. Processor 230 then determines which pre-coding matrix to usefor determining the beamforming weights then processes the extractedmessage.

Turning to FIG. 3, this figure shows an alternative simplifiedfunctional block diagram of a communication device according to oneembodiment of the invention. As shown in FIG. 3, the communicationdevice 300 in a wireless communication system can be utilized forrealizing the UEs (or ATs) 116 and 122 in FIG. 1, and the wirelesscommunications system is preferably the LTE system. The communicationdevice 300 may include an input device 302, an output device 304, acontrol circuit 306, a central processing unit (CPU) 308, a memory 310,a program code 312, and a transceiver 314. The control circuit 306executes the program code 312 in the memory 310 through the CPU 308,thereby controlling an operation of the communications device 300. Thecommunications device 300 can receive signals input by a user throughthe input device 302, such as a keyboard or keypad, and can outputimages and sounds through the output device 304, such as a monitor orspeakers. The transceiver 314 is used to receive and transmit wirelesssignals, delivering received signals to the control circuit 306, andoutputting signals generated by the control circuit 306 wirelessly. Thecommunication device 300 in a wireless communication system can also beutilized for realizing the AN 100 in FIG. 1.

FIG. 4 is a simplified block diagram of the program code 312 shown inFIG. 3 in accordance with one embodiment of the invention. In thisembodiment, the program code 312 includes an application layer 400, aLayer 3 portion 402, and a Layer 2 portion 404, and is coupled to aLayer 1 portion 406. The Layer 3 portion 402 generally performs radioresource control. The Layer 2 portion 404 generally performs linkcontrol. The Layer 1 portion 406 generally performs physicalconnections.

The DOCOMO 5G White Paper introduces a 5G radio access concept thatefficiently integrates both lower and higher frequency bands. Sincehigher frequency bands provide opportunities for wider spectrum but havecoverage limitations because of higher path loss, it was proposed that a5G system has a two-layer structure which consists of a coverage layer(e.g., consisting of macro cells) and a capacity layer (e.g., consistingof small cells or phantom cells). The coverage layer uses existing lowerfrequency bands to provide basic coverage and mobility. The capacitylayer uses new higher frequency bands to provide high data ratetransmission. The coverage layer could be supported by enhanced LTE RAT(Long Term Evolution Radio Access Technology), while the capacity layercould be supported by a new RAT dedicated to higher frequency bands.Furthermore, integration of the coverage and capacity layers is enabledby the tight interworking (e.g., dual connectivity) between the enhancedLTE RAT and the new RAT.

Dual connectivity is a mode of operation for a UE (User Equipment) inRRC_CONNECTED, configured with a Master Cell Group and a Secondary CellGroup as discussed in 3GPP R2-145410. A Master Cell Group is a group ofserving cells associated with the MeNB (Master Evolved Node B),comprising of the PCell (Primary Cell) and optionally one or more SCell(Secondary Cell). A Secondary Cell Group is a group of serving cellsassociated with the SeNB (Secondary Evolved Node B), comprising of aSpCell (Special Cell) and optionally one or more SCell (Secondary Cell).A UE configured with dual connectivity generally means that the UE isconfigured to utilize radio resources that are provided by two distinctschedulers, and located in two eNBs (MeNB and SeNB) connected via anon-ideal backhaul over the X2 interface. Furthermore, C-plane messagesare communicated via MeNB. Further details of dual connectivity can befound in 3GPP R2-145410.

In dual connectivity, a random access (RA) procedure may be performedupon SCG (Secondary Cell Group) addition, DL (downlink) data arrival,and UL (uplink) data arrival to achieve uplink synchronization. Thereare two different types of RA procedures: contention-based RA andcontention-free RA.

A contention based RA procedure is shown in FIG. 5 and includes thefollowing four steps:

1. Random Access Preamble is transmitted by UE on RACH (Random AccessChannel), and is mapped to PRACH (Physical Random Access Channel);

2. Random Access Response is received from eNB on DL-SCH (DownlinkShared Channel), and is mapped to PDSCH (Physical Uplink SharedChannel);

3. Scheduled Transmission is transmitted by UE on UL-SCH (Uplink-SharedChannel), and is mapped to PUSCH (Physical Uplink Shared Channel); and

4. Contention Resolution is received from eNB on PDCCH (PhysicalDownlink Control Channel) or on DL-SCH, and is mapped to PDSCH.

A contention-free RA procedure is shown in FIG. 6 and includes thefollowing three steps:

1. Random Access Preamble assignment is received from eNB (evolved NodeB);

2. Random Access Preamble is transmitted by UE on UL-SCH (Uplink-SharedChannel), and is mapped to PUSCH; and

3. Random Access Response is received from eNB on DL-SCH (DownlinkShared Channel), and is mapped to PDSCH.

After transmitting a RA preamble, a UE shall monitor a PDCCH for RAresponse(s) from an eNB (i.e., a base station) in a RA response window,which starts at the subframe (or TTI (Transmission Time Interval)) thatcontains the end of the preamble transmission plus three subframes andhas length ra-ResponseWindowSize subframes, as discussed in 3GPP TS36.321 V12.3.0. If the UE does not receive a valid RA response from theeNB within the RA response window, the UE shall retransmit a RA preambleuntil the maximum number of retransmissions has been reached or a validRA response is received. Thus, it might take more than one run tocomplete a RA procedure. Details of a RA procedure can be found in 3GPPR2-145410 and TS 36.321 V12.3.0.

In the current LTE RAT, a UE periodically transmits a sounding referencesymbol/signal (SRS) for channel quality estimation to enablefrequency-selective scheduling on the uplink. Thus, the resources forSRS transmissions cover wider bandwidth. Details of a UE soundingprocedure can be found in 3GPP TS 36.213 V12.3.0.

Cells on the capacity layer may use beam forming, which is a signalprocessing technique used in antenna arrays for directional signaltransmission or reception. This is achieved by combining elements in aphased array in such a way that signals at particular angles experienceconstructive interference while others experience destructiveinterference. Beam forming can be used at both the transmitting andreceiving ends in order to achieve spatial selectivity. The improvementcompared with omnidirectional reception/transmission is known as thereceive/transmit gain.

The benefit of cochannel interference reduction and radio resource reusemakes beam forming attractive to a mobile communication system designer.U.S. Patent Publication No. 2010/0165914 generally discloses the conceptof beam division multiple access (BDMA) based on the beam formingtechnique. In BDMA, a base station can communicate with a UE via anarrow beam to obtain the receive/transmit gain. Also, two UEs indifferent beams can share the same radio resources at the same time; andthus the capacity of a mobile communication system can increase greatly.To achieve that, the base station should know the beam in which a UE cancommunicate with the base station.

Furthermore, U.S. Pat. No. 7,184,492 generally discloses using beamforming antenna to coherently transmit an information signal to areceiver using two or more directional beams. In one embodiment, thephase and timing of the information signals carried by each directionalbeams are adjusted such that the signals arrive synchronously at themobile terminal. Time synchronization may be obtained by delayingsignals transmitted on selected directional beams to compensate fordifferent propagation delays, or by preconditioning and filtering thesignals using a channel coefficient matrix.

As discussed in 3GPP TS 36.300 V12.5.0, the frame structure in LTE isorganized into radio frames and each radio frame (e.g., 10 ms), and isdivided into ten subframes. As stated in 3GPP TS 36.300 V12.5.0, eachsubframe may include two slots as follows:

5 Physical Layer for E-UTRA

Downlink and uplink transmissions are organized into radio frames with10 ms duration. Two radio frame structures are supported:

Type 1, applicable to FDD;

Type 2, applicable to TDD.

Frame structure Type 1 is illustrated in FIG. 5.1-1 [which has beenreproduced as FIG. 7 of the present application]. Each 10 ms radio frameis divided into ten equally sized sub-frames. Each sub-frame consists oftwo equally sized slots. For FDD, 10 subframes are available fordownlink transmission and 10 subframes are available for uplinktransmissions in each 10 ms interval. Uplink and downlink transmissionsare separated in the frequency domain.

FIG. 5.1-1 has been Reproduced as FIG. 7 of the Present Application

Frame structure Type 2 is illustrated in FIG. 5.1-2 [which has beenreproduced as FIG. 8 of the present application]. Each 10 ms radio frameconsists of two half-frames of 5 ms each. Each half-frame consists ofeight slots of length 0.5 ms and three special fields: DwPTS, GP andUpPTS. The length of DwPTS and UpPTS is configurable subject to thetotal length of DwPTS, GP and UpPTS being equal to 1 ms. Both 5 ms and10 ms switch-point periodicity are supported. Subframe 1 in allconfigurations and subframe 6 in configuration with 5 ms switch-pointperiodicity consist of DwPTS, GP and UpPTS. Subframe 6 in configurationwith 10 ms switch-point periodicity consists of DwPTS only. All othersubframes consist of two equally sized slots.For TDD, GP is reserved for downlink to uplink transition. OtherSubframes/Fields are assigned for either downlink or uplinktransmission. Uplink and downlink transmissions are separated in thetime domain.

FIG. 5.1-2 has been Reproduced as FIG. 8 of the Present ApplicationTable 5.1-1 “Uplink-Downlink Allocations” has been Reproduced as FIG. 9of the Present Application

Each downlink slot includes N_(symb) ^(DL) OFDM symbols as shown in FIG.6.2.2-1 (which has been reproduced as FIG. 10 of the presentapplication) and in Table 6.2.3-1 (which has been reproduced as FIG. 11of the present application) of 3GPP TS 36.211 V12.5.0. FIG. 6.2.2-1 of3GPP TS 36.211 V12.5.0 has been reproduced as FIG. 10 of the presentapplication. Table 6.2.3-1 “Physical resource blocks parameters” of 3GPPTS 36.211 V12.5.0 has been reproduced as FIG. 11 of the presentapplication.

A TDD (Time Division Duplex) optimized physical subframe structure for aUDN (Ultra Dense Network) system proposed by METIS Deliverable D2.4“Proposed solutions for new radio access” is illustrated in FIG. 12while following the main design principles listed below:

-   -   A bi-directional (including both DL and UL resources) control        part is embedded to the beginning of each subframe and        time-separated from data part.    -   Data part in one subframe contains data symbols for either        transmission or reception. Demodulation Reference Signal (DMRS)        symbols, which are used to estimate the channel and its        covariance matrix, could be located, for example, in the first        OFDM (Orthogonal Frequency-Division Multiplexing) symbol in the        dynamic data part and could be precoded with the same vector or        matrix as data.    -   Short subframe lengths, such as e.g. 0.25 ms on cmW frequencies        when assuming 60 kHz SC spacing, are feasible. By following the        principles of harmonized OFDM concept, the frame numerology is        further scaled when moving to mmW, leading to even shorter frame        length (e.g., in the order of 50 μs).    -   In frequency direction, the spectrum could be divided to        separate allocable frequency resources.

The bi-directional control part of the subframe allows the devices inthe network to both receive and send control signals, such as schedulingrequests (SRs) and scheduling grants (SGs), in every subframe. Inaddition to the scheduling related control information, the control partmay also contain reference signals (RS) and synchronization signals usedfor cell detection and selection, scheduling in frequency domain,precoder selection, and channel estimation.

To find beam(s) in which a UE can communicate with a base station, it isproposed in US Patent Publication No. 2010/0165914 that the UE transmitsits position and speed to the base station, and the base station thendetermines the direction of a downlink beam for the UE according to thereceived position and speed. In this way, however, the base station maynot able to determine the UE's beams accurately, due to the verycomplicated propagation environment in mobile cellular systems. Inaddition, typically not all UEs in a cell are equipped with positioningcapability (e.g., low end devices). As a result, the benefit of BDMA(Beam Division Multiple Access) cannot be enjoyed if there are many lowend devices in a cell. Other ways for a base station to determine UE'sbeams could and should be considered to improve this drawback.

A potential beam pattern applied by a base station for transmissionand/or reception in a cell could be fixed as shown in FIG. 13. That isthe number of beams and the beam-widths of beams in a cell are fixed,while the beam-widths of beams in different directions could bedifferent. Due to multiple propagation paths or overlapping between twoneighboring beams, it is likely that multiple beams would be used by aUE for communicating with the base station. In this situation, the basestation needs to determine the beam set used by a UE (e.g., bymonitoring an uplink signal transmitted from the UE).

Since a random access (RA) procedure needs to be performed by a UEbefore data can be transferred via a cell, it would be beneficial forthe base station to determine the initial beam set of a UE during the RAprocedure, especially if a dedicated RA preamble is used. For example,the beam set could be determined according to the beam(s) via which thededicated RA preamble(s) is (are) received from the UE.

Considering the enlarged number of antennas with wider bandwidth, it isquite challenging in terms of overall cost and power consumption toimplement beam forming in a cell with one transceiver per antennaelement. As a result, the maximum number of beams which could begenerated by a cell at one time could be less than the total number ofbeams covered by a cell. Thus, it may take several times for the cell toscan all beams of the cell. In this situation, the base station wouldmiss a dedicated RA preamble transmitted from a UE if none of the beamspoints to the direction of the UE when the RA preamble is transmitted.As a result, several runs of random access may be required tosuccessfully complete a RA procedure, which would cause latency to thesubsequent data transfer via the cell. In addition, resource sharingbetween the concerned UE and other UEs in the cell would be delayed.This is undesirable.

To reduce the latency, a potential solution is for a UE to transmitmultiple RA preambles in a short period of time before it startsmonitoring a PDCCH for RA response(s) from the base station. The basestation would then be allowed to complete scanning all beams of the cellso as to receive at least one RA preamble from the UE. With thissolution, a RA procedure could be successfully completed without toomuch latency. FIG. 14 shows an example of this solution according to oneexemplary embodiment.

In FIG. 14, it is assumed the UE is located in beams X and Y. The basestation monitors preambles at T1, T2, and T3 for receiving preambles viadifferent beams of the cell. In this example, multiple beams could bemonitored at each time. The preamble transmitted by the UE is receivedvia beams X and Y at T2. Thus, the beam set of the UE is {X, Y}. It ispossible that preambles transmitted by the UE could be received atdifferent times. On the other hand, the base station does not transmitany RA response to the UE until all the multiple beams of the cell hasbeen monitored. In other words, the base station transmits a RA responseto the UE after all beams of the cell has been monitored if there is anyRA preamble received.

Preferably, the base station could determine a beam set of the UEaccording to the beam(s) via which RA preamble(s) is (are) received fromthe UE. After the initial beam set of a UE has been determined, the basestation needs to continue tracking the UE and update the beam set due toUE mobility. It seems possible for the base station to track the beamset of a UE based on periodic SRS-like reference signal (RS)transmissions from the UE, wherein it could be sufficient for theSRS-like RS to cover narrower bandwidth. Then, the beam set could beupdated according to the beam(s) via which the RS(s) is (are) receivedfrom the UE. More precisely, a potential solution is for the UE totransmit multiple RSs in each period, which would allow the base stationto complete scanning all beams of the cell in a short time so as toreceive at least one RS from the UE for updating the beam set of the UE.FIG. 15 illustrates an example of this solution according to oneexemplary embodiment.

In FIG. 15, a UE periodically transmits RSs for beam set update after aninitial beam set of the UE has been determined by a base station. Duringthe first period, the base station monitors RS at T1, T2, and T3 viadifferent beams of the cell and RS is received via beams X and Y at T2.The beam set of the UE is updated to {X, Y}. Due to UE mobility, RS isreceived via beam Z alone at T6 during the second period. As a result,the new beam set is {Z}. In this example, multiple beams are monitoredat each time. It is also possible that RSs transmitted by the UE couldbe received at different times.

In general, there could be two different ways for the base station tocontrol beam set tracking, including a distributed way and a centralizedway. In the distributed way, each UE would be tracked individually at UEspecific times and is allocated with RS resources, wherein the RSresources define periodic resources for RS transmissions and there aremultiple occasions with resources for transmissions of multiple RSs bythe UE in each RS period. In one embodiment, an occasion refers to atime unit (e.g., a symbol, a time slot, or a subframe).

In the centralized way, all UEs (which need to be tracked in the cell)are tracked at common occasions so that the base station only needs tomonitor those occasions to receive RSs transmitted by all UEs. In oneembodiment, all UEs share one RS period. In another embodiment, UEs mayhave different RS periods, while timings of all RS periods aresynchronized. For example, there is a nominal RS period and a RS periodof each UE is a multiple of the nominal RS period. FIG. 16 showsexamples of these two options. For Option 1, all UEs share one RS periodand the base station needs to monitor RSs from all UEs in each RS period(i.e., the tracking period=the RS period), while the base station needsto monitor RSs from UEs in each nominal RS period (i.e., the trackingperiod=the nominal RS period×1) for Option 2 (i.e., UE specific RSperiod). In one embodiment, each occasion of a RS period is shared byall UEs which need to be tracked (in case there are sufficient RSresources on each occasion for all UEs). In another embodiment,different occasions of the RS period are occupied by different UEs.

If digital beam-former is used for implementing a cell, there would beno problem to have one transceiver per antenna element i.e. all beams ofthe cell can be generated at one time. Thus, each UE would only need totransmit a single RS for base station to determine the beam set of theUE. Similar methods for beam tracking described above for a cell withanalog beam-former are also applicable to a cell with digitalbeam-former. In this situation (i.e., a cell with digital beam-former),the base station would only need to allocate RS resources to each UE forone single RS transmission on one occasion in each RS period for beamtracking if digital beam-former is used. It is possible that all UEsshare one RS period or UEs may have different RS periods. In oneembodiment, each occasion of a RS period is shared by all UEs which needto be tracked. In another embodiment, different occasions of the RSperiod are occupied by different UEs.

A TDD optimized physical subframe structure for a UDN system is proposedby METIS Deliverable D2.4 “Proposed solutions for new radio access”. Ingeneral, there are one uplink control part, one downlink control part,and one data part as shown in FIG. 12. To support BDMA, an uplinkcontrol part may need to contain PUCCH (Physical Uplink Control Channel)signaling for HARQ ACK/NACK (Hybrid Automatic Repeat RequestAcknowledgement/Negative Acknowledgement) and RS for UE beam setdetection. The UE would send a HARQ ACK/NACK in response to a downlinktransmission from a base station. Since PUCCH signaling for HARQACK/NACK and RS for UE beam set detection may be transmitted bydifferent UEs and received by the base station via different beams, itis more flexible in term of scheduling to have at least two symbols inthe uplink control part: (1) one symbol contains RS resources for UEbeam set detection and (2) another symbol not contain any RS resourcefor UE beam set detection. In one embodiment, the symbol which containsRS resources for UE beam set detection may also contain resources forHARQ ACK/NACK signaling. This embodiment would be feasible if thebeam(s) used by the base station to receive PUCCH signaling for HARQACK/NACK is the same as the beam(s) used for monitoring RS for UE beamset detection. Otherwise, the base station may miss the PUCCH signalingfor HARQ ACK/NACK, which would degrade the transmission performance.

FIG. 17 is a flow chart 1700, in accordance with one exemplaryembodiment, outlining a method for preamble transmissions by a UE in acell of a wireless communication system, wherein there are multiplebeams in the cell. In step 1705, the UE initiates a random access (RA)procedure. In step 1710, the UE transmits multiple RA preambles to abase station of the cell at different occasions for the base station todetermine a beam set of the UE.

In step 1715, the UE starts monitoring a Physical Downlink ControlChannel (PDCCH) for RA response reception from the base station afterfinishing transmissions of the multiple RA preambles. In one embodiment,the UE monitors the PDCCH for RA response reception in a RA responsewindow. Furthermore, the RA response window could start at a subframethat contains an end of a transmission of the last RA preamble of themultiple RA preambles plus a number of subframes and has a lengthconfigured to the UE. More specifically, the RA response window couldstart at a subframe that contains the end of the transmission of thelast RA preamble transmission plus three (3) subframes. Furthermore, theUE could receive one RA response for the UE within the RA responsewindow.

In one embodiment, the UE could decode each RA response individuallywithout combining multiple RA responses. In another embodiment, the UEcould be within normal coverage of the base station, such as thereceived signal quality of the UE from the base station is above athreshold, so that the UE could decode each RA response individuallywithout combining multiple RA responses.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a UE, the device 300 includes a program code 312 stored in memory 310of the transmitter. The CPU 308 could execute program code 312 (i) toinitiate a RA procedure, (ii) to transmit multiple RA preambles to abase station of the cell at different occasions for the base station todetermine a beam set of the UE, and (iii) to start monitoring a PhysicalDownlink Control Channel (PDCCH) for RA response reception from the basestation after finishing transmissions of the multiple RA preambles. Inaddition, the CPU 308 can execute the program code 312 to perform all ofthe above-described actions and steps or others described herein.

FIG. 18 is a flow chart 1800 from the perspective of a base station inaccordance with one exemplary embodiment. In general, the flow chart1800 outlines a method for beam finding in a cell of a wirelesscommunication system, wherein there are multiple beams in the cell. Instep 1805, a base station of the cell monitors RA preamble(s) viadifferent beams at different occasions during a RA procedure. In step1810, the base station receives at least a RA preamble from a UE. Instep 1815, the base station determines a beam set of the UE according tothe beam(s) via which the RA preamble(s) is (are) received.

In step 1820, the base station transmits a RA response to the UE afterall the multiple beams of the cell have been monitored. In oneembodiment, the base station transmits only one RA response to the UE inresponse to receptions of multiple RS preambles from the UE during theRA procedure. Furthermore, multiple beams are monitored at eachoccasion. In addition, an occasion refers to a time unit (e.g., asymbol, a time slot, or a subframe).

In one embodiment, the RA preamble is dedicated to the UE. In addition,the RA preamble being dedicated to the UE could mean the RA preamble ofthe UE is distinguishable from RA preambles of other UEs in the cell inat least one of following domains: time domain, frequency domain, andsequence domain.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a base station, the device 300 includes a program code 312 stored inmemory 310 of the transmitter. The CPU 308 could execute program code312 (i) to monitor RA preamble(s) via different beams at differentoccasions during a RA procedure, (ii) to receive at least a RA preamblefrom a UE, and (iii) to determine a beam set of the UE according to thebeam(s) via which the RA preamble(s) is (are) received. In addition, theCPU 308 could execute program code 312 to transmit a RA response to theUE after all the multiple beams of the cell have been monitored.Furthermore, the CPU 308 can execute the program code 312 to perform allof the above-described actions and steps or others described herein.

FIG. 19 is a flow chart 1900, in accordance with one exemplaryembodiment, outlining a method for determining a beam set used by a UEin a cell of a wireless communication system, wherein there are multiplebeams in the cell. In general, the method outlined in the flow chart1900 could be applied by a base station in distributed and centralizedsettings.

In step 1905, the UE is allocated with reference signal (RS) resourceson the cell, wherein the RS resources define periodic resources for RStransmissions, and there are multiple occasions with resources fortransmissions of multiple RSs by the UE in each RS period. In step 1910,a base station of the cell uses at least one beam to receive a RStransmitted from the UE on each occasion in a RS period. In oneembodiment, the base station uses different sets of beams to receive RSstransmitted from the UE on different occasions in the RS period.Furthermore, the total beams could be used to receive RSs transmittedfrom the UE in the RS period cover all beams of the cell.

In one embodiment, the multiple occasions could be UE specific. In analternative embodiment, the multiple occasions could be shared by UEswhich need to be tracked.

Referring back to FIGS. 3 and 4, the device 300 includes a program code312 stored in memory 310 of the transmitter. The CPU 308 could executeprogram code 312 (i) to enable the UE to be allocated with RS resourceson the cell, wherein the RS resources define periodic resources for RStransmissions, and there are multiple occasions with resources fortransmissions of multiple RSs by the UE in each RS period, and (ii) toenable a base station to use at least one beam to receive a RStransmitted from the UE on each occasion in a RS period. In addition,the CPU 308 can execute the program code 312 to perform all of theabove-described actions and steps or others described herein.

FIG. 20 is a flow chart 2000, in accordance with one exemplaryembodiment, outlining a method for determining beam sets used by UEs ina cell of a wireless communication system, wherein each UE has its ownbeam set and there are multiple beams in the cell. In general, themethod outlined in the flow chart 2000 could be applied by a basestation in a centralized setting and to the same RS period for all UEs.

In step 2005, each UE is allocated with reference signal (RS) resourceson the cell, wherein the RS resources define periodic resources for RStransmissions, there are multiple occasions with resources fortransmissions of multiple RSs by each UE in each RS period, and one RSperiod is shared by UEs which need to be tracked. In step 2010, a basestation of the cell uses at least one beam to receive RSs transmittedfrom UEs on each occasion in the RS period, wherein the total beams usedto receive the RSs transmitted from UEs in the RS period cover all beamsof the cell.

In one embodiment, the base station determines the beam set used by theUE according to the beam(s) via which RS(s) is (are) received from theUE. In another embodiment, the base station could transmit a message toallocate the RS resources to the UE (for single connectivity). In analternative embodiment, a second base station of a second cell servingthe UE could transmit a message to allocate the RS resources to the UE(for dual connectivity).

In one further embodiment, the beam set used by a UE contains at leastone beam. Furthermore, an occasion refers to a time unit (e.g., asymbol, a time slot, or a subframe).

Referring back to FIGS. 3 and 4, the device 300 includes a program code312 stored in memory 310 of the transmitter. The CPU 308 could executeprogram code 312 (i) to enable each UE to be allocated with RS resourceson the cell, wherein the RS resources define periodic resources for RStransmissions, there are multiple occasions with resources fortransmissions of multiple RSs by each UE in each RS period, and one RSperiod is shared by UEs which need to be tracked, and (ii) to enable abase station of the cell to use at least one beam to receive a RStransmitted from the UE on each occasion in a RS period. In addition,the CPU 308 can execute the program code 312 to perform all of theabove-described actions and steps or others described herein.

FIG. 21 is a flow chart 2100, in accordance with one exemplaryembodiment, outlining a method for determining beam sets used by UEs ina cell from the perspective of a UE. In general, the method outlined inthe flow chart 2100 could be applied by a base station in a centralizedsetting and to a UE-specific RS period.

In step 2105, each UE is allocated with reference signal (RS) resourceson the cell, wherein the RS resources define periodic resources for RStransmissions, there are multiple occasions with resources fortransmissions of multiple RSs by each UE in each RS period, and a RSperiod of each UE is a multiple of a nominal RS period. In step 2110, abase station of the cell uses at least one beam to receive RSstransmitted from UEs on each occasion in a tracking period, wherein thetotal beams used to receive the RSs transmitted from UEs in the trackingperiod cover all beams of the cell. In one embodiment, the trackingperiod could be determined according to the RS periods of UEs which needto be tracked. Furthermore, the tracking period could be a multiple ofthe nominal RS period. In addition, the tracking period could be equalto the nominal RS period.

In step 2115, the base station determines the beam set used by the UEaccording to the beam(s) via which RS(s) is (are) received from the UE.In one embodiment, the base station could transmit a message to allocatethe RS resources to the UE (for single connectivity). In an alternativeembodiment, a second base station of a second cell serving the UE couldtransmit a message to allocate the RS resources to the UE (for dualconnectivity).

In one embodiment, the beam set used by a UE contains at least one beam.Furthermore, an occasion refers to a time unit (e.g., a symbol, a timeslot, or a subframe).

Referring back to FIGS. 3 and 4, the device 300 includes a program code312 stored in memory 310 of the transmitter. The CPU 308 could executeprogram code 312 (i) to enable each UE to be allocated with RS resourceson the cell, wherein the RS resources define periodic resources for RStransmissions, there are multiple occasions with resources fortransmissions of multiple RSs by each UE in each RS period, and a RSperiod of each UE is a multiple of a nominal RS period, (ii) to enable abase station of the cell to use at least one beam to receive RSstransmitted from UEs on each occasion in a tracking period, wherein thetotal beams used to receive the RSs transmitted from UEs in the trackingperiod cover all beams of the cell, and (iii) to enable the base stationto determine the beam set used by the UE according to the beam(s) viawhich RS(s) is (are) received from the UE. In addition, the CPU 308 canexecute the program code 312 to perform all of the above-describedactions and steps or others described herein.

FIG. 22 is a flow chart 2200, in accordance with one exemplaryembodiment, outlining a method for RS transmissions by a UE in a cell ofa wireless system. In step 2205, the UE receives a message indicatingreference signal (RS) resources on a cell, wherein the RS resourcesdefine periodic resources for RS transmissions, and there are multipleoccasions with resources for transmissions of multiple RSs by the UE ineach RS period. In step 2110, the UE transmits multiple RSs in each RSperiod to a base station of the cell.

In one embodiment, the UE could receive the message from the basestation (for single connectivity). Alternatively, the UE could receivethe message from a second base station of a second cell serving the UE(for dual connectivity). In addition, there could be multiple beams inthe cell.

In one embodiment, an occasion could refer to a time unit in FDD(Frequency Division Duplex) mode (e.g., a symbol, a time slot, or asubframe). Alternatively, an occasion could refer to a time unit in TDD(Time Division Duplex) mode (e.g., a symbol in a normal subframe, a timeslot, or a subframe). Furthermore, the multiple occasions could becontiguous, and each occasion of a RS period could be shared by all UEswhich need to be tracked. In addition, different occasions of the RSperiod could be occupied by different UEs.

In one embodiment, the RSs could be dedicated to a particular UE, whichmeans the RSs of the particular UE are distinguishable from RSs of otherUEs in the cell in at least one of following domains: time domain,frequency domain, and/or sequence domain.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a UE, the device 300 includes a program code 312 stored in memory 310of the transmitter. The CPU 308 could execute program code 312 (i) toreceive a message indicating reference signal (RS) resources on a cell,wherein the RS resources define periodic resources for RS transmissions,and there are multiple occasions with resources for transmissions ofmultiple RSs by the UE in each RS period, and (ii) to transmit multipleRSs in each RS period to a base station of the cell. In addition, theCPU 308 can execute the program code 312 to perform all of theabove-described actions and steps or others described herein.

FIG. 23 is a flow chart 2300, in accordance with one exemplaryembodiment, outlining a method for determining beam sets used by UEs ina cell of a wireless system, wherein each UE has its own beam set andthere are multiple beams in the cell. In general, the method outlined inthe flow chart 2300 could be applied by a base station in a centralizedsetting and to the same RS period for all UEs.

In step 2305, each UE is allocated with periodic RS resources on thecell for RS transmissions, wherein UEs which need to be tracked in thecell share one RS period. In step 2310, a base station of the cell usesall beams of the cell to receive RSs transmitted from UEs on eachoccasion with RS resources in each RS period. In one embodiment, the RSresources in each RS period for UEs which need to be tracked are locatedin one subframe. Furthermore, there is at least one occasion with RSresources in each RS period.

In step 2315, the base station determines the beam set used by the UEaccording to the beam(s) via which RS(s) is (are) received from the UE.In one embodiment, the base station could transmit a message to allocatethe RS resources to the UE (for single connectivity). Furthermore, asecond base station of a second cell serving the UE could transmit amessage to allocate the RS resources to the UE (for dual connectivity).

In one embodiment, the beam set used by a UE contains at least one beam.In addition, the RSs are dedicated to the UE, which means the RSs of theUE are distinguishable from RSs of other UEs in the cell in at least oneof following domains: time domain, frequency domain, and sequencedomain.

In one embodiment, an occasion refers to a time unit e.g. a symbol, atime slot, or a subframe. Furthermore, each occasion of a RS periodcould be shared by all UEs which need to be tracked. In addition,different occasions of the RS period could be occupied by different UEs.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a base station, the device 300 includes a program code 312 stored inmemory 310 of the transmitter. The CPU 308 could execute program code312 (i) to allocate each UE with periodic RS resources on the cell forRS transmissions, wherein UEs which need to be tracked in the cell shareone RS period, and (ii) to enable a base station of the cell to use allbeams of the cell to receive RSs transmitted from UEs on each occasionwith RS resources in each RS period.

In one embodiment, the CPU 308 could further execute program code 312 toenable the base station to determine the beam set used by the UEaccording to the beam(s) via which RS(s) is (are) received from the UE.In addition, the CPU 308 can execute the program code 312 to perform allof the above-described actions and steps or others described herein.

FIG. 24 is a flow chart 2400, in accordance with one exemplaryembodiment, outlining a method for determining beam sets used by UEs ina cell of a wireless system, wherein each UE has its own beam set andthere are multiple beams in the cell. In general, the method outlined inthe flow chart 2400 could be applied by a base station in a centralizedsetting and to a UE-specific RS period.

In step 2405, each UE is allocated with periodic RS resources on thecell for RS transmissions, wherein a RS period of the UE is a multipleof a nominal RS period. In step 2410, a base station of the cell usesall beams of the cell to receive RSs transmitted from UEs on eachoccasion with RS resources in each tracking period.

In one embodiment, the RS resources in each tracking period for UEswhich need to be tracked are located in one subframe. Furthermore, thereis at least one occasion with RS resources in each tracking period.

In one embodiment, the tracking period is determined according to the RSperiods of UEs which need to be tracked in the cell. Furthermore, thetracking period is a multiple of the nominal RS period. In addition, thetracking period is equal to the nominal RS period.

In step 2415, the base station determines the beam set used by the UEaccording to the beam(s) via which RS(s) is (are) received from the UE.In one embodiment, the base station could transmit a message to allocatethe RS resources to the UE (for single connectivity). Furthermore, asecond base station of a second cell serving the UE could transmit amessage to allocate the RS resources to the UE (for dual connectivity).

In one embodiment, the beam set used by a UE contains at least one beam.In addition, the RSs are dedicated to the UE, which means the RSs of theUE are distinguishable from RSs of other UEs in the cell in at least oneof following domains: time domain, frequency domain, and sequencedomain.

In one embodiment, an occasion refers to a time unit e.g. a symbol, atime slot, or a subframe. Furthermore, each occasion of a RS periodcould be shared by all UEs which need to be tracked. In addition,different occasions of the RS period could be occupied by different UEs.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a base station, the device 300 includes a program code 312 stored inmemory 310 of the transmitter. The CPU 308 could execute program code312 (i) to allocate each UE with periodic RS resources on the cell forRS transmissions, wherein a RS period of the UE is a multiple of anominal RS period, and (ii) to enable a base station of the cell to useall beams of the cell to receive RSs transmitted from UEs on eachoccasion with RS resources in each tracking period.

In one embodiment, the CPU 308 could further execute program code 312 toenable the base station to determine the beam set used by the UEaccording to the beam(s) via which RS(s) is (are) received from the UE.In addition, the CPU 308 can execute the program code 312 to perform allof the above-described actions and steps or others described herein.

FIG. 25 is a flow chart 2500, in accordance with one exemplaryembodiment, outlining a method for defining a subframe structure forbeam detection. In step 2505, a cell communicates with UEs in the cellvia downlink transmissions and uplink receptions, wherein the downlinktransmissions and uplink receptions are organized into radio frames. Instep 2510, a radio frame is constructed with multiple subframes, whereina subframe in the radio frame includes at least an uplink control part,and the uplink control part includes at least: (1) a first symbol, whichis allocated with resources for the UEs to transmit reference signalsfor the cell to determine beam sets of the UEs, and (2) a second symbol,which is not allocated with resources for the UEs to transmit thereference signals for the cell to determine beam set of the UEs.

In one embodiment, a first symbol is allocated with resources for HARQACK/NACK (Hybrid Automatic Repeat Request Acknowledgement/NegativeAcknowledgement) signaling in step 2515. Furthermore, a second symbol isallocated with resources for HARQ ACK/NACK signaling in step 2520.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a cell, the device 300 includes a program code 312 stored in memory310 of the transmitter. The CPU 308 could execute program code 312 (i)to enable a cell to communicate with UEs via downlink transmissions anduplink receptions, wherein the downlink transmissions and uplinkreceptions are organized into radio frames, and (ii) to construct aradio frame with multiple subframes, wherein a subframe in the radioframe includes at least an uplink control part, and the uplink controlpart includes at least: (1) a first symbol, which is allocated withresources for the UEs to transmit reference signals for the cell todetermine beam sets of the UEs, and (2) a second symbol, which is notallocated with resources for the UEs to transmit the reference signalsfor the cell to determine beam sets of the UEs.

In one embodiment, the CPU 308 could further execute program code 312 toallocate the first symbol and the second symbol with resources for HARQACK/NACK signaling. In addition, the CPU 308 can execute the programcode 312 to perform all of the above-described actions and steps orothers described herein.

FIG. 26 is a flow chart 2600, in accordance with one exemplaryembodiment, outlining a method for defining a subframe structure forbeam detection. In step 2605, a UE communicates with a cell via uplinktransmissions and downlink receptions, wherein the uplink transmissionsand downlink receptions are organized into radio frames. In step 2610, aradio frame is constructed with multiple subframes, wherein a subframein the radio frame includes at least an uplink control part, and theuplink control part includes at least: (1) a first symbol, which isallocated with resources for the UE to transmit reference signals forthe cell to determine a beam set of the UE, and (2) a second symbol,which is not allocated with resources for the UE to transmit thereference signals for the cell to determine the beam set of the UE.

In one embodiment, a first symbol is allocated with resources for HARQACK/NACK signaling in step 2615. Furthermore, a second symbol isallocated with resources for HARQ ACK/NACK signaling in step 2520.

Referring back to FIGS. 3 and 4, in one embodiment from the perspectiveof a UE, the device 300 includes a program code 312 stored in memory 310of the transmitter. The CPU 308 could execute program code 312 (i) toenable a UE to communicate with a cell via uplink transmissions anddownlink receptions, wherein the uplink transmissions and downlinkreceptions are organized into radio frames, and (ii) to construct aradio frame with multiple subframes, wherein a subframe in the radioframe includes at least an uplink control part, and the uplink controlpart includes at least: (1) a first symbol, which is allocated withresources for the UE to transmit reference signals for the cell todetermine a beam set of the UE, and (2) a second symbol, which is notallocated with resources for the UE to transmit the reference signalsfor the cell to determine the beam set of the UE.

In one embodiment, the CPU 308 could further execute program code 312 toallocate the first symbol and the second symbol with resources for HARQACK/NACK signaling. In addition, the CPU 308 can execute the programcode 312 to perform all of the above-described actions and steps orothers described herein.

With respect to the methods outlined in FIGS. 25 and 26, in oneembodiment, the subframe in the radio frame could contain a downlinkcontrol part and/or a data part. Furthermore, the subframe structurecould be used in a TDD (Time Division Duplex) mode.

In one embodiment, the downlink transmissions and uplink receptionsrelevant to the UE could be performed by the cell on multiple beams in abeam set of the UE. Furthermore, a total number of beams in the cellcould be fixed. In addition, the direction and/or the width of each beamin the cell could be fixed

In one embodiment, there is a period associated with transmissions ofthe reference signals and there are multiple resources for referencesignal transmissions at different occasions (or timings) in each period.

Various aspects of the disclosure have been described above. It shouldbe apparent that the teachings herein may be embodied in a wide varietyof forms and that any specific structure, function, or both beingdisclosed herein is merely representative. Based on the teachings hereinone skilled in the art should appreciate that an aspect disclosed hereinmay be implemented independently of any other aspects and that two ormore of these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. As an exampleof some of the above concepts, in some aspects concurrent channels maybe established based on pulse repetition frequencies. In some aspectsconcurrent channels may be established based on pulse position oroffsets. In some aspects concurrent channels may be established based ontime hopping sequences. In some aspects concurrent channels may beestablished based on pulse repetition frequencies, pulse positions oroffsets, and time hopping sequences.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, processors, means, circuits, and algorithmsteps described in connection with the aspects disclosed herein may beimplemented as electronic hardware (e.g., a digital implementation, ananalog implementation, or a combination of the two, which may bedesigned using source coding or some other technique), various forms ofprogram or design code incorporating instructions (which may be referredto herein, for convenience, as “software” or a “software module”), orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

In addition, the various illustrative logical blocks, modules, andcircuits described in connection with the aspects disclosed herein maybe implemented within or performed by an integrated circuit (“IC”), anaccess terminal, or an access point. The IC may comprise a generalpurpose processor, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, electrical components, opticalcomponents, mechanical components, or any combination thereof designedto perform the functions described herein, and may execute codes orinstructions that reside within the IC, outside of the IC, or both. Ageneral purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of a sample approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The steps of a method or algorithm described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module (e.g., including executable instructions and relateddata) and other data may reside in a data memory such as RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a harddisk, a removable disk, a CD-ROM, or any other form of computer-readablestorage medium known in the art. A sample storage medium may be coupledto a machine such as, for example, a computer/processor (which may bereferred to herein, for convenience, as a “processor”) such theprocessor can read information (e.g., code) from and write informationto the storage medium. A sample storage medium may be integral to theprocessor. The processor and the storage medium may reside in an ASIC.The ASIC may reside in user equipment. In the alternative, the processorand the storage medium may reside as discrete components in userequipment. Moreover, in some aspects any suitable computer-programproduct may comprise a computer-readable medium comprising codesrelating to one or more of the aspects of the disclosure. In someaspects a computer program product may comprise packaging materials.

While the invention has been described in connection with variousaspects, it will be understood that the invention is capable of furthermodifications. This application is intended to cover any variations,uses or adaptation of the invention following, in general, theprinciples of the invention, and including such departures from thepresent disclosure as come within the known and customary practicewithin the art to which the invention pertains.

The invention claimed is:
 1. A method for preamble reception by a basestation of a cell of a wireless communication system, wherein there aremultiple beams in the cell, the method comprising: the base stationscans multiple timings, at which multiple random access (RA) preamblesare transmitted by a User Equipment (UE) in the cell, with all beams ofthe cell so that at least one RA preamble from the UE is received by thebase station; and the base station transmits an RA response to the UEafter finishing scanning the multiple timings with all beams of the celland finishing reception of the at least one RA preamble.
 2. The methodof claim 1, wherein the RA response is transmitted to the UE via aPhysical Downlink Control Channel (PDCCH) in a RA response window. 3.The method of claim 2, wherein the RA response window starts at asubframe that contains an end of a transmission of a last RA preamble ofthe multiple RA preambles plus a number of subframes and has a lengthconfigured to the UE.
 4. The method of claim 3, wherein the RA responsewindow starts at a subframe that contains the end of the transmission ofthe last RA preamble of the multiple RA preambles plus three (3)subframes.
 5. The method of claim 2, wherein the RA response windowstarts at a subframe that has a length configured to the UE.
 6. Themethod of claim 1, wherein each of the multiple timings refers to asymbol.
 7. The method of claim 1, wherein each of the multiple timingsrefers to a time slot.
 8. The method of claim 1, wherein the UE iswithin normal coverage of the base station such that a received signalquality of the UE from the base station is above a threshold.
 9. Themethod of claim 1, wherein each of the multiple timings refers to asubframe.
 10. The method of claim 1, wherein the base station scans themultiple timings with all beams of the cell in association with the UE.11. The method of claim 1, wherein the base station scans the multipletimings with all beams of the cell in association with receiving one ormore RA preambles from the UE.
 12. A base station a cell of a wirelesscommunication system, the base station comprising: a control circuit; aprocessor installed in the control circuit; and a memory installed inthe control circuit and operatively coupled to the processor; whereinthe processor is configured to execute a program code stored in thememory to: scan multiple timings, at which multiple random access (RA)preambles are transmitted by a User Equipment (UE) in the cell, with allbeams of the cell so that at least one RA preamble from the UE isreceived by the base station; and transmit an RA response to the UEafter finishing scanning the multiple timings with all beams of the celland finishing reception of the at least one RA preamble.
 13. The UE ofclaim 12, wherein the RA response is transmitted to the UE via aPhysical Downlink Control Channel (PDCCH) in a RA response window. 14.The UE of claim 13, wherein the RA response window starts at a subframethat contains an end of a transmission of a last RA preamble of themultiple RA preambles plus a number of subframes and has a lengthconfigured to the UE.
 15. The UE of claim 14, wherein the RA responsewindow starts at a subframe that contains the end of the transmission ofthe last RA preamble of the multiple RA preambles plus three (3)subframes.
 16. The UE of claim 12, wherein each of the multiple timingsrefers to a symbol.
 17. The UE of claim 12, wherein each of the multipletimings refers to a time slot.
 18. The UE of claim 12, wherein each ofthe multiple timings refers to a subframe.
 19. The UE of claim 12,wherein the base station scans the multiple timings with all beams ofthe cell in association with the UE.
 20. The UE of claim 12, wherein thebase station scans the multiple timings with all beams of the cell inassociation with receiving one or more RA preambles from the UE.